The present invention relates to a room temperature curing polyorganosiloxane composition which can be stored stably in the absence of moisture for a long period of time without curing but which is cured by moisture to form an elastomer when it is allowed to stand in air. Particularly, the present invention relates to a room temperature curing polyorganosiloxane composition having improved curing properties which releases an oxime compound upon curing.
Room temperature curing polyorganosiloxane compositions are well known and the constituents of which are generally kept in a closed vessle but the composition will cure by exposure to moisture in the air thereby releasing an oxime compound. Such a composition does not have an irritating smell due to the released substance and does not corrode metals substantially, nor will it affect alkaline substances such as mortar as compared with other polyorganosiloxane compositions which generate acetic acid upon curing into an elastomer. Therefore, the former materials have been used widely as sealing materials, adhesives, and coating materials in the construction, electric, electronic, automotive industries, etc. However, as compared with the acetic acid-releasing compositions, the oxime compound-releasing compositions have a lower curing velocity and relatively longer times are required for forming rubbery films on surfaces. Thus, the oxime compound-releasing compositions which require longer times for working and treatment are less satisfactory, and it has long been an object to overcome such defects.
Among processes for increasing the curing velocity or cure rate of these polyorganosiloxane compositions which release an oxime compound upon curing to form an elastomer, there has been proposed a process in the specification of Japanese Patent Laid-Open No. 116424/1977 wherein an oxime radical-containing silane is used as a cross-linking agent wherein at least one of the organic radicals bonded with a silicon atom via a silicon-carbon bond is substituted with a monocarboxylic acid residue in which the hydrocarbon radical may be unsubstituted or substituted with a halogen atom, a nitro radical, an alkoxyl radical or a cyano radical. However, in practice, this silane compound has disadvantages in that special materials are required for the synthesis thereof and the synthesis is difficult. Under these circumstances, the development of a cross-linking agent which can be synthesized more easily and which can increase the curing velocity and which also can be used for the production of a room temperature curing polyorganosiloxane composition of the oxime compound-releasing type has been sought.
The present invention relates to an improvement in curing velocity for polyorganosiloxane compositions which release an oxime compound upon curing. An object of the invention is therefore to provide a composition which forms a rubbery, cured film on a surface in a short period of time upon contact with moisture in the air.